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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: crh1415 on March 20, 2006, 07:56:27 PM

Title: Ions in Electrolyes Help Needed
Post by: crh1415 on March 20, 2006, 07:56:27 PM
Hey there, I'm having some serious problems with my homework assignment.

I'm supposed to:

"Calculate the concentraion of all ions present in each of the following solutions of strong electrolytes"

The first problem is:

0.300 mol of Ca(NO3)2 in 100.0 mL of solution

Honestly, I'm totally clueless as to where to begin. I know that the two ions I need to calculate the molarity for are Ca2+ and NO3-

To begin would I divide 0.300 moles by 0.100 L to get the overall molarity?

All help is appreciated!
Title: Re:Ions in Electrolyes Help Needed
Post by: Borek on March 20, 2006, 08:07:19 PM
Quote from: crh1415 on March 20, 2006, 07:56:27 PM
To begin would I divide 0.300 moles by 0.100 L to get the overall molarity?

Yes. Don't forget that there are twice more NO3- then Ca2+.
Title: Re:Ions in Electrolyes Help Needed
Post by: mike on March 20, 2006, 08:08:36 PM
c = n/v so when you divide the number of moles of Ca(NO3)2 by the volume this will give you the concentration in solution of Ca(NO3)2. For every one mole of Ca(NO3)2 in solution you have one mole of Ca2+ and two moles of NO3-. Which means that the concetration of Ca2+ should be the same as Ca(NO3)2 and the concentration of NO3- should be twice the concentration of Ca(NO3)2
Title: Re:Ions in Electrolyes Help Needed
Post by: crh1415 on March 20, 2006, 08:39:32 PM
Ok great, thank you very much for the help Borek and Mike!